The present invention relates to a method for operating an agricultural working machine, in particular a forage harvester.
Publication DE 35 05 887 makes known a method for regulating crop-material throughput that regulates the throughput performance of an agricultural working machine designed as a forage harvester by monitoring the rotational speed of the chopper drum. According to the method disclosed therein, the drive engine of the forage harvester is operated in the usual manner in an engine speed range in which the maximum engine output is available. The preselectable rotational speed of the chopper drum fluctuates depending on the crop-material throughput to be processed by the agricultural working machine and the available engine output.
When the rotational speed of the chopper drum falls below a preset minimum value, suitable regulating devices reduce the ground speed and, therefore, the quantity of newly picked-up crop material until the rotational speed of the chopper drum returns to a rotational speed range that is above the preset minimum value. In an analogous manner, the ground speed of the agricultural working machine is increased when the torque provided by the available engine power is above the torque required to operate the forage harvester. Threshold values are used in this case as well that induce a change in the ground speed of the forage harvester if they are exceeded or fallen below.
A similar method for regulating throughput on a forage harvester is described in EP 1 051 898. In this case, the drive engine is to be operated at a nearly constant engine speed, while the crop-material throughput to be processed by the agricultural working machine is regulated as a function of the torque that corresponds to the nearly constant engine output and is provided by the drive engine. This regulation is carried out such that the ground speed is adjusted—i.e., reduced, if overload occurs—or the rotational speed of the intake rollers is changed, i.e., reduced, if overload occurs. It is also provided that fuzzy logic is used for this purpose.
Both of these methods have the disadvantage that the drive engine is always operated in the range of high engine speeds, which result in a rapid acceleration of the crop material, since the gear ratios between the drive engine and the working units it drives are typically fixed. The crop material is therefore conveyed through the agricultural working machine at a high rate of speed. The greater the quantity is of crop material—i.e., the crop-material throughput—to be conveyed, the greater is the portion of power required to accelerate the crop material and overcome the friction—which is proportional to speed—of the crop material inside the agricultural working machine. Both of these effects greatly limit the possibilities for increasing the crop-material throughput and, due to the high engine speed, result in the need to operate the drive engine of the agricultural working machine in a range of increased fuel consumption.